What do the number levels mean when you our tanning at a tanning salon?

Is it less burnig rays the higher the level and safer? (example level 4)What do the number levels mean when you our tanning at a tanning salon?
My daughter worked for a tanning salon. If you filled out an application when you began, it would give you a number for your skin type, and then reccomend the safe tanning for you. You could also mean, the intensity levels of the lamps for the beds? http://www.yearroundbrown.com/article-highandlow.html


Hope this helps you out.